Polymeric stent and method of manufacture

Abstract

A stent formed of polymeric material, useful for the expansion of a lumen and the delivery of one or more therapeutic agents in situ is disclosed. The stent may be multi-layered, and may change shape at a state transition temperature governed by the materials forming the layers. Methods of use and manufacture are also disclosed.

1 . A method of forming an implantable prosthesis, comprising:
 forming an extruded polymer that is formed into a structure having a first diameter at a first temperature;   radially altering the structure to have a second diameter which is different from the first diameter; and   cooling the structure to a second temperature lower than the first temperature such that the second diameter is set in the structure.   
   
   
       2 . The method of  claim 1  wherein forming comprises extruding a continuous film of polymer. 
   
   
       3 . The method of  claim 1  wherein forming further comprises cooling the polymer to a temperature at or below the first temperature. 
   
   
       4 . The method of  claim 1  wherein the first temperature, T 1 , is determined whereby T 1 =T g +X° C., where T g  is a glass transition temperature of the polymer and X is from about −20 to about +120. 
   
   
       5 . The method of  claim 4  wherein the second temperature, T 2 , is determined whereby T 2 =T 1 −Y° C., and Y is from about 5 to about 80. 
   
   
       6 . The method of  claim 1  wherein forming comprises forming the structure to have a helical shape. 
   
   
       7 . The method of  claim 1  wherein radially altering the structure comprises applying a force to the structure such that the diameter is altered from the first diameter to the second diameter. 
   
   
       8 . The method of  claim 1  wherein radially altering the structure comprises urging the structure from the first diameter, D 1 , to the second diameter, D 2 , wherein D 2 <D 1 . 
   
   
       9 . The method of  claim 1  further comprising mixing an agent which is miscible with the polymer prior to extruding. 
   
   
       10 . The method of  claim 1  further comprising adding a therapeutic agent to the polymer prior to extruding. 
   
   
       11 . The method of  claim 10  wherein said therapeutic agent is selected from the group consisting of a drug, an antibiotic, an anti-inflammatory agent, an anti-clotting factor, a hormone, a nucleic acid, a peptide, a cellular factor, a ligand for a cell surface receptor, an anti-proliferative agent, an antithrombotic agent, an antimicrobial agent, an anti-viral agent, a chemotherapeutic agent, and an anti-hypertensive agent. 
   
   
       12 . The method of  claim 1  wherein the polymer comprises a biostable polymer selected from the group consisting of polyethylene, polypropylene, polyethylene terephthalate (PET), polyurethane poly(ether urethane), poly(ester urethane), poly vinyl chloride, polyvinyl acetate (PVAc), poly(ethylene-co-vinyl acetate) (PEVAc), polycaprolactone and Nylon 6,6. 
   
   
       13 . The method of  claim 1  wherein the polymer comprises a bioabsorbable polymer selected from the group consisting of poly-L-lactide (PLLA), poly-D-lactide (PDLA), polyglycolide (PGA), polylactide-co-glycolide (PLGA), polydioxanone, polygluconate, polylactic acid-polyethylene oxide copolymer, modified cellulose, collagen, poly(hydroxybutyrate), polyanhydride, polyphosphoester and poly-amino acid. 
   
   
       14 . A method of inducing stability into an implantable prosthesis, comprising:
 forming a structure at a first temperature from an extruded polymer such that the structure defines a first diameter;   setting the first diameter in the structure;   reconfiguring the structure at a second temperature lower than the first temperature to define a second diameter different from the first diameter; and   setting the second diameter in the structure.   
   
   
       15 . The method of  claim 14  wherein forming comprises extruding a continuous polymer film. 
   
   
       16 . The method of  claim 14  wherein setting the first diameter comprises cooling the polymer to a temperature at or below the first temperature. 
   
   
       17 . The method of  claim 14  wherein reconfiguring comprises applying a force to the structure such that the diameter is altered from the first diameter to the second diameter. 
   
   
       18 . The method of  claim 14  wherein reconfiguring comprises urging the structure from the first diameter, D 1 , to the second diameter, D 2 , wherein D 2 <D 1 . 
   
   
       19 . The method of  claim 14  further comprising adding a therapeutic agent to the polymer prior to forming. 
   
   
       20 . A method of forming an implantable prosthesis, comprising:
 forming a co-extruded polymer having a first and a second layer, wherein the first layer comprises a first polymer having a glass transition temperature T g1  and wherein the second layer comprises a second polymer having a glass transition temperature T g2 ;   forming a structure having a first diameter at a first temperature;   radially altering the structure to have a second diameter which is different from the first diameter; and   cooling the structure to a second temperature lower than the first temperature such that the second diameter is set in the structure.   
   
   
       21 . The method of  claim 20  wherein co-extruding comprises extruding the first layer and second layer independently of one another. 
   
   
       22 . The method of  claim 21  further comprising attaching the first layer and second layer to one another via an attachment mechanism selected from the group consisting of thermal bonding, solvent bonding, adhesive bonding, mechanical friction, and combinations thereof. 
   
   
       23 . The method of  claim 20  wherein that the first layer forms an outer surface of the structure and the second layer forms an inner surface of the structure. 
   
   
       24 . The method of  claim 20  wherein radially altering comprises applying a force to the structure such that the diameter is altered from the first diameter to the second diameter. 
   
   
       25 . An implantable prosthesis, comprising:
 a substrate having a first polymer that is at least partially amorphous and has a glass transition temperature T g1 , and a second polymer that is at least partially amorphous and has a glass transition temperature T g2 ,   wherein the substrate is formed as a structure from a co-extruded polymer such that the structure has an inner surface and an exterior surface for contacting a vessel wall, and   wherein the structure is formed to have a first shape at a first temperature and a second shape at a second temperature different from the first temperature and configured to change from said first shape to said second shape at a temperature equal to or greater than a transition temperature.   
   
   
       26 . The method of  claim 25  wherein co-extruding comprises extruding the first layer and second layer independently of one another. 
   
   
       27 . The method of  claim 26  further comprising attaching the first layer and second layer to one another via an attachment mechanism selected from the group consisting of thermal bonding, solvent bonding, adhesive bonding, mechanical friction, and combinations thereof. 
   
   
       28 . The prosthesis of  claim 25  wherein the structure is formed from the first shape to the second shape when urged via application of a force.